Part Number: AM3359
Hi,
I have a custom board running on Linux which has a 6MB external RAM connected to the GPMC. I can interact with the GPMC Registers and it seems to be ok, for example if I write into the reset register then it triggers the reset done register. However, I can't access the external memory and I don't know what I'm missing here. First of all I would like to share my device tree configuration and ask a few questions:
I slightly modified the am33xx.dtsi to have access to the external memory through UIO
soc {
compatible = "ti,omap-infra";
mpu {
compatible = "ti,omap3-mpu";
ti,hwmods = "mpu";
pm-sram = <&pm_sram_code
&pm_sram_data>;
};
dpram_mem: dpram_mem {
compatible = "ti,uio-module-drv";
mem = <0x08000000 0x600000>; // dpram
mem-names = "dpram";
status = "disabled";
};
};
Then the GMPC part of my board looks as follows:
&gpmc {
status = "okay";
pinctrl-names = "default";
pinctrl-0 = <&triport_pins_default>;
/* chip select ranges */
ranges = <0 0 0x08000000 0x600000>; //6MB RAM: 0x600000
sram {
compatible="mtd-ram";
reg = <0 0 0x08000000>; /*CSn0*/
bank-width = <2>; /* GPMC_CONFIG1_DEVICESIZE(1) */
/*gpmc,burst-write;*/
/*gpmc,burst-read;*/
/*gpmc,burst-wrap;*/
gpmc,sync-read; /* GPMC_CONFIG1_READTYPE_ASYNC */
gpmc,sync-write; /* GPMC_CONFIG1_WRITETYPE_ASYNC */
gpmc,clk-activation-ns = <0>; /* GPMC_CONFIG1_CLKACTIVATIONTIME(2) */
gpmc,burst-length = <16>; /* GPMC_CONFIG1_PAGE_LEN(2) */
gpmc,mux-add-data = <2>; /* GPMC_CONFIG1_MUXTYPE(2) */
gpmc,sync-clk-ps = <20000>; /* CONFIG2 */
gpmc,cs-on-ns = <0>;
gpmc,cs-rd-off-ns = <130>;
gpmc,cs-wr-off-ns = <100>;
gpmc,adv-on-ns = <0>; /* CONFIG3 */
gpmc,adv-rd-off-ns = <45>;
gpmc,adv-wr-off-ns = <45>;
gpmc,we-on-ns = <45>; /* CONFIG4 */
gpmc,we-off-ns = <50>;
gpmc,oe-on-ns = <45>;
gpmc,oe-off-ns = <100>;
//gpmc,page-burst-access-ns = <20>; /* CONFIG 5 */
gpmc,access-ns = <100>;
gpmc,rd-cycle-ns = <145>;
gpmc,wr-cycle-ns = <95>;
gpmc,wr-access-ns = <45>; /* CONFIG 6 */
gpmc,wr-data-mux-bus-ns = <20>;
/*gpmc,bus-turnaround-ns = <40>;*/ /* CONFIG6:3:0 = 4 */
gpmc,cycle2cycle-samecsen; /* CONFIG6:7 = 1 */
gpmc,cycle2cycle-delay-ns = <20>; /* CONFIG6:11:8 = 4 */
};
};
&dpram_mem {
status = "okay";
};
First of all I wonder with the sram compatible parameter. I set "mtd-ram". I tried first without the compatible parameter but it does not work. Then I tried with mtd-ram and mtd-nor... I guess I need to set something there, otherwise Linux wont be able to load a proper driver to access the external memory. Is my device tree ok? Should I modify something there?
Other than that, this is the configuration I have under Linux:
dmesg | grep gpmc [ 3.117132] omap-gpmc 50000000.gpmc: GPMC revision 6.0 [ 3.122416] gpmc_mem_init: disabling cs 0 mapped at 0x0-0x1000000 [ 3.130037] gpio gpiochip4: (omap-gpmc): added GPIO chardev (254:4) [ 3.130610] gpiochip_setup_dev: registered GPIOs 510 to 511 on device: gpiochip4 (omap-gpmc) [ 3.132625] gpmc_read_settings_dt: page/burst-length set but not used!
cat /proc/iomem ...... 50000000-50001fff : gpmc@50000000 ......
When the uio_module_drv is loaded, it generates the device for the external memory. So I can open the device and map the memory.
[ 37.570012] uio_module_drv soc:dpram_mem: registered misc device dpram_mem
However when I ran my application I get this:
/dev/mem opened. Memory mapped at address 0xb6f94000. /dev/dpram_mem opened. Memory mapped at address 0xb67e5000. Bus error
/dev/mem is used to map the GPMC registers and it works fine. The dpram_mem is used to map the 0x08000000 memory range, where the external memory should be located, but however I get a bus error and the application crashes.
I followed these topics and documentation as reference:
https://e2e.ti.com/support/processors/f/791/t/512464
https://e2e.ti.com/support/processors/f/791/p/315716/1510538
https://e2e.ti.com/support/processors/f/791/p/793386/2960137
Any hint with this issue?
Many thanks in advance,
Alvaro
